Hermetically sealed food package

ABSTRACT

PACKAGE COMPRISES A FLANGED CONTAINER OF SEMI-RIGID, GAS-IMPERMEABLE, TRANSPARENT PLASTIC CONTAINING A FOOD PRODUCT AND A SHEET OF STRETCHABLE GAS-IMPREABLE FILM SEALED TO THE FLANGES. THE PACKAGE IS EVACUATED PRIOR TO SEALING AND CAN INCLUDE AN INERT GAS ATMOSPHERE. A RIGID BOARD IS ATTACHED TO THE FILM AT THE FLANGE AREA WITH A BOND STRONGER THAN THAT BETWEEN THE FILM AND CONTAINER. APPARATUS FOR FORMING THE PACKAGE INCLUDES A FIRST PACKAGING STATION WHERE THE FILM IS SEALED AROUND A PORTION OF THE FLANGE AREA BY HEAT SEAL BARS AND VACUUM MEANS TO DRAW THE FILM INTERIOR OF THE FLANGE TOWARD A HEATING ELEMENT INTERIORR OF THE SEAL BARS. SECOND PACKAGING STATION INCLUDES MEANS TO EVACUATE THE PACKAGE, COMPLETE THE SEAL BETWEEN THE FILM AND THE CONTAINER, AND A CHECK VALVE WHICH VENTS THE AREA ABOVE THE FILM WHILE MAINTAINING THE VACUUM BELOW THE CONTAINER. THE ATMOSPHERIC PRESSURE CAUSES THE STRETCHED FILM TO BE PASSED INTO TIGHT FITTING CONTACT WITH THE UPPER SURFACE OF THE FOOD PRODUCT.

Jan. 9, 1973 R. A. MAHAFFY ETAL 3,709,702

HERMETICALLY SEALED FOOD PACKAGE Original Filed Sept. 1, 1965 3Sheets-Sheet 1 INVENTORS R/ed JLMahaffy Joel A. Hamilon Wesley WPzLnneBY j M 74 ATTORNEYS Jan. 9, 1973 MAHAFFY ETAL HERMETICALLY SEALED FOODPACKAGE Original Filed Sept. 1. 1965 s Sheets-Sheet 2"I'IIIIIIIIIIIIIII.

J 9, 1973 R. A. MAHAF'FY ETAL 3,709,702

, HERMETICALLY SEALED FOOD PACKAGE Original Filed Sept. 1, 1965 3Sheets-Sheet 3 Patented Jan. 9, 1973 3,709,702 HERMETICALLY SEALED FOODPACKAGE Reid A. Mahaffy, Montclair, Joel A. Hamilton, Clifton,

US. Cl. 99174 7 Claims ABSTRACT OF THE DISCLOSURE Package comprises aflanged container of semi-rigid, gas-impermeable, transparent plasticcontaining a food product and a sheet of stretchable gas-impermeablefilm sealed to the flanges. The package is evacuated prior to scalingand can include an inert gas atmosphere. A rigid board is attached tothe film at the flange area with a bond stronger thanpthat between thefilm and container. Apparatus for forming the package includes a firstpackaging station where the film is sealed around a portion of theflange area by heat seal bars and vacuum means to draw the film interiorof the flange toward a heating element interior of the seal bars. Secondpackaging station includes means to evacuate the package, complete theseal between the film and the container, and a check valve which ventsthe area above the film while maintaining the vacuum below thecontainer. The atmospheric pressure causes the stretched film to bepressed into tight fitting contact with the upper surface of the foodproduct.

This application is a continuation of Ser. No. 484,284, filed onSeptember 1, 1965, and now abandoned.

This invention relates to packaging food products and the like inhermetically-sealed containers. More particularly, this inventionrelates to improved automatic packaging apparatus, packaging methods,and the packages made thereby.

Reference is made to copending application Ser. No. 64,034, filed by W.E. Young et al., on July 22, 1970, showing basic subject matter of thepresent application. To clarify the relationship between these twoapplications, it is noted that said copending application is directed tothe broad packaging concepts wherein a semi-rigid evacuated packagecomprising a cup-like receptacle or container is provided with astretch-formed top arranged to reduce the transmittal of distortingstresses from the top to the container cup. Such package may be formedwith a sequenced pressure application wherein pressure first is appliedto the top and thereafter to the semi-rigid bottom. The top may bestretched subsequent to package evacuation, as by application ofatmospheric pressure upon venting the evacuation chamber, or the top maybe prestretched prior to assembly and completion of the package, as byapplication of differential pressure prior to the evacuation phase ofthe package operation. This application, on the other hand, is directedto specific features including (a) a trapezoidal-like bacon packageconfiguration, (b) the use of a stiff protective member as a thirdpackage element, and bonding techniques therefor, (c) the techniquewherein the top is stretched by first moving it away from the semi-rigidcontainer (and the product contained therein) to a region adjacent aheater, and thereafter forcing the top towards the container to stretchit, and (d) the use of a check valve to obtain the sequencedpressure-application technique more broadly claimed in said copendingapplication.

For a number of years now, extensive use has been made of automaticapparatus for packaging products in evacuated containers formed offlexible plastic packaging material. In some cases, the products wereinserted in preformed pouches which were then evacuated and sealed alongthe opening. Subsequently (see, for example, US. Pat. 3,061,984),completely automatic machines were developed to form packages from twosheets of flexible plastic film drawn from respective supply rolls. Ineither case, the resulting container was formed entirely of thinflexible film. Thus the ultimate evacuation of the container caused thefilm to be forced inwardly by atmospheric pressure into close andintimate pressure-contact with the enclosed product, and distorting thefilm into a shape conforming to the product profile.

For many products, such as luncheon meat and frankfurters, this approachprovided reasonably acceptable results. However, it was not reallysatisfactory for certain other types of products. For example, whenpackaging a shingled group of bacon slices it has been found that thepressure applied by the atmosphere through the film to all parts of thebacon tends to cause undesirable cohesion of the individual strips ofbacon after the container is opened by the purchaser. Also, theresulting container does not afford prospective customers the bestpresentation of the bacon through the stretched and distorted parts ofthe film.

Accordingly, it is one object of this invention to provide an evacuatedpackage which is superior to those available heretofore. Another objectof this invention is to provide improved vacuum packaging apparatus andmethods. Still another object of this invention is to provide noveltechniques for packaging certain specialty products such as bacon. Otherobjects, aspects and advantages of this invention will in part bepointed out in, and in part apparent from, the following descriptionconsidered together with the accompanying drawings, in which:

FIG. 1 is a longitudinal vertical section through a part of thepackaging machine;

FIG. 2 is a detail horizontal section (from below), showing thepreliminary sealing means of the packaging head;

FIG. 3 is a perspective view of a completed package;

FIG. 4 is a cross-section taken along line 4-4 of FIG. 3;

FIG. 5 is a detail view, greatly magnified, of one corner of FIG. 4;

FIG. 6 is a detail view, like FIG. 5, but showing a modified packageconstruction; and

FIG. 7 is a perspective view showing the package of FIG. 6 with its topfolded back.

Referring now to FIG. 1, the packaging apparatus comprises a series oftrays 10 each adapted to receive and snugly support a correspondingcup-like receptacle 12 carrying the product 14, in this case a one poundshingled group of bacon slices. These trays are power-driven from rightto left with an intermittent cyclical indexing movement to permitcertain sequential packaging operations to be performed at respectivestations along the path of movement.

Receptacles 12 are made of transparent, calendere'd non-plasticizedpolyvinyl chloride, advantageously having a thickness in the range offive to fifteen mils. Such polyvinyl chloride is semi-rigid, meaningthat it is self-supporting and substantially retains its shape undernormal conditions of use, e.g. with a normal product load such as mightbe simulated by filling the receptacle with water. The receptacles arein the shape of a truncated triangular prism, best illustrated in FIG.3, and having a cross-section in the form of an isosceles trapezoid asshown in FIG. 4. The receptacles are formed with flat peripheral flanges16 extending entirely around the opening, and lying in a common plane.

Above two adjacent positions of the trays 10 is a packaging headgenerally indicated at 18 and mounted (by conventional means, not shown)for vertical reciprocating movement in synchronism with the indexing ofthe trays. That is, when the trays stop, head 18 moves down to carry outcertain operations to be described, and then rises just before the nextindexing movement, so as to permit the trays to be shifted horizontallywithout interference.

To the right of packaging head 18, a web of flexible plastic packagingfilm 20 descends vertically to a lay down roll 21. This roll aids inapplying the film to the top of the trays as they are shifted into thefirst position under the packaging head 18. The film is drawn from asupply roll (not shown) and has a Width suflicient to cover thereceptacles 12 including the side flanges thereof. In the disclosedembodiment, film 20.is a laminate of sarancoated polyester and polyvinylchloride, and the polyvinyl chloride side faces down to engage thepolyvinyl chloride receptacles 12. Thus the heat-sealing properties ofthe film are compatible with those of the receptacles and both provide agood oxygen barrier.

The packaging head 18 includes both a preliminary seal means, generallyindicated at 22, and an evacuation and final seal means, generallyindicated at 24. The preliminary seal means further comprises peripheralheat-sealing bars 26 (see FIG. 2) arranged to extend around threeflanges of the receptacle 12 and partially along the fourth flange. Thegap in the heat-sealing bar along the fourth flange is filled with a lowthermal conductivity, heat-re sistant elastomer 28, e.g. siliconerubber, the lower edge of which is in the same plane as the heat sealingbars, or projects slightly below. Thus, when the head 18 descends, itpresses the film 20 tightly against all of the flanges 16, sealing thefilm against air leakage around the entire periphery of the preliminarysealing means.

Also carried by the packaging head 18, within the preliminary seal means22, is a flat platen the lower surface of which is about /s" above theplane of the heatsealing bars 26. The Side edges of this platen arespaced a small distance from the interior side walls of the heatsealingbars. This platen is formed to receive a set of heater elements 32,additional to the sealing heaters 33, to maintain the platen at amoderately elevated temperature.

When the packaging head 18 is in its lower position, the chamber definedby the preliminary sealing means 22 is evacuated by a vacuum line 36. Asshown in FIG. 1, this causes the film 20 to be forced uniformly upagainst the platen 30 so that the film becomes somewhat softened by theheat. Such softening makes it readily possible, by application ofreasonable pressure, to stretch the film, e.g. beyond its elastic limit,for purposes as will be described subsequently.

While the receptacle 12 is in the preliminary seal position, the heatedbars 26 operate in known manner to heat-seal the film 20 to thecorresponding receptacle 12 along three of the flanges 16. Since theelastomer 28 is not heated, that end of the receptacle is not sealed tothe film.

The head 18 thereafter rises and the partially sealed receptacle 12 isindexed to the next position Where the evacuation and final sealing ofthe package take place. To this end, each tray 10 is provided with acaptive weblifter 38 which, in accordance with prior. art techniques, isshifted up (through a previously formed cut-out 12a in the receptacle12) to raise the end of the film 20 opposite the unsealed flange of thereceptacle. The package then is evacuated through the channel thuscreated between the film and the receptacle. The vacuum is drawn throughthe web-lifter passage in the tray, through a vertically reciprocablegasketed coupler 40, a line 42 including a check valve 44 and the mainvacuum valve 46 to which is connected a vacuum conduit 48. This mainvalve 46 also connects vacuum through a line 50 to the chamber above thefilm 20.

After evacuation, main valve 46 is shut oh and an inert gas is admittedinto the package from a gas line 52. The gas passes through an internalconduit in the Web-lifter support, and exits into the package through anaperture in the top of the web-lifter. When the proper amount of gas hasbeen admitted, the web-lifter is allowed to drop back down to its normalrest position and the usual heated final seal bar descends from abovethe the film 20 to complete the heat-sealing of the film to thereceptacle 12. This final seal extends along the side of the receptacleinteriorly of the aperture 12a, and overlaps the preliminary seal linesso as to make the package completely gas-proof.

Thereafter, main valve 46 is shifted to its vent position, admittingatmospheric air through line 50 into the final seal chamber above thefilm 20. The check valve 44 momentarily restrains the flow of air intothe trays 10, but the air pressure above and below the package equalizesfairly quickly because some air will flow downward into the web-lifterpassage which is imperfectly closed off by the final seal bar in itslowered position. In some cases, it may be desirable to speed up thispressure equalization by providing an adjustable-restriction by-passvalve around the check valve 44.

Although the foregoing description applies particularly to packagingmachines of the type where evacuation is effected at one end of thepackage, this invention also is applicable to machines of the centerevacuation type as illustrated in US. Pat. 3,061,984. For such centerevacuation machines, two assemblies as illustrated in FIG. 2 are used ina side-by-side relationship with the elastomers 28 adjacent each other.The operation is identical, except that during venting to atmosphere noair will pass from the final seal chamber to the web-lifter passagesince there is no exposed edge of the film around which it can pass.Hence the air that is admitted to the final seal chamber is somewhatmore effective in forming the film downward into the trays 12. It alsomay particularly be desirable to bleed air slowly through a by-passvalve around check valve 44 so that the coupler 40 will not adhere tothe tray.

The inrush of atmospheric pressure above the film 20 serves to forcethis film down into the receptacle 12, causing the film to be stretched.The extent of stretching depends upon how much gas had previously beenadmitted into the package. Preferably, the admission of gas is adjustedto that amount which results in the edges of the bacon being pressedlightly against the interior surface of the receptacle 12 when thepackage is in its normal upright position as shown in FIG. 3.

The stretching of the film 20 interiorly of the flanges 16 is aided bythe heat applied in the preceding preliminary seal operation. Thus thefilm is somewhat softened so that it can be stretched, advantageously toan amount resulting in a permanent set of the plastic material. In anyevent, the film is force-fitted and stretched by the atmosphericpressure around all of the contours of the exposed pieces of bacon. Thereceptacle 12, being made of semi-rigid material, is not so formed aboutthe bacon but instead contacts the edges of the bacon with the desiredpressure engagement sufficient to assure that the bacon is immobilizedwithin the package. This arrangement particularly is advantageousbecause shifting of the bacon can smear grease on the interior of thereceptacle and interfere with a prospective customers inspection of theproduct.

The pressure of the product against the interior of the receptacle 12should be suflicient to press any large flat product surfaces, such asthat of the end slice 14a, into full contact with the interior of thereceptacle. However, the pressure desirably is low enough to avoidsquashing the bacon edges 14b flat against that interior. This degree ofpressure provides a superior package appearance while preventingshifting of the product, disarray and grease smearing.

The film 20 can be vacuum-formed, i.e. stretched beyond its elasticlimit, while in the preliminary sealing stage, for example to such anextent that no further stretching is needed in the final seal stage.Such stretching may be useful in some ap lications, and is facilita d bythe effective air-tight seal around all four sides at the preliminaryseal means, as well as by the heat transferred to the film by the platen30. When forming the film in the preliminary sealing position, theplaten 30 advantageously is placed more than /s" above the plane of theheat sealing bars 26, e.g. at a distance approximately equal to theextent of forming desired. For some applications, the need forpre-heating and/or pre-stretching the film may be reduced or evenavoided, as by the use of film material having suitable characteristicsof stretchability at normal ambient operating temperatures.

In the final seal stage, physical stretching of the interior marginalportions of the film 20 inwardly to the product 14, especially to apermanent set dimension, is desirable because it tends to eliminate anysubstantial buildup of tension in the film. As shown in FIG. 5, the filmis formed inwardly at 20a to follow the side wall contour of thereceptacle 12. Thus the force of the atmospheric pressure is carriedessentially by the packaged product, aided by the internal gas pressure.This avoids placing portions of the package under heavy stress, andminimizes distortion of the semi-rigid receptacle from its originalshape.

FIGS. 6 and 7 show a modified package construction suitable for certainparticular applications. The basic arrangement is generally the same, inthat the package comprises a semi-rigid plastic member 12 (serving asthe top in the normal upright position of the package) sealed around itsflanges 16 to the plastic film 20 to form an evacuated container. Afterthe package-making operations are completed as in the first embodiment,a paper board member 60 is secured to the film 20. This board is thickerthan film 20, preferably between 5 and 12 mils, thus providingadditional rigidity. Advantageously, the board is secured to the filmaround all of the marginal edges, as by means of a sealant 62, and canbe so secured while the evacuated container is still in its tray 10. Thesealant 62 can for example be of the type which is activated byconventional heating means.

Preferably, this sealant 62 forms a bond substantially stronger thanthat between film 2.0 and semi-rigid member 12. By this means, itbecomes more readily possible to open the package simply by peeling thefilm and paper board, as a unit, away from the semi-rigid member 12, asshown in FIG. 7.

'One side of the semi-rigid member 12 is formed with a finger tab 64 toaid in opening the package. When the package is opened, the board 60will bend about a longitudinal line running along the back of thepackage, the board being somewhat pliable relative to the semi-rigidmember 12. The first embodiment of the invention (FIG. 3) also mayinclude a finger tab 64 to aid in peeling the film 20 away from thesemi-rigid member.

The manifold arrangement of FIGS. 6 and 7 provides a package which notonly is more rigid, but the addition of the paper board minimizes thechances that the package might be punctured, e.g. in shipment orhandling. The presence of the board also makes the package easier toopen; after the desired number of bacon slices have been removed, thepackage may readily be closed and returned to the refrigerator forstorage.

When the package is first opened, the relief of the vacuum permits thefilm 20 to fall down to the level of the paper board 60. When thepackage is reclosed for storage of remaining bacon, it is possible toplace the package in a stack of similar packages, or to place otherarticles on top without injuring the remaining product. Before thepackage is opened, it also is well adapted to stacking, the flexiblefilm 20 acting as a diaphragm-like spring.

Although in the preferred embodiment described herein, the film 20 isdrawn up to heated platen 30 by vacuum, this upward film movement can beobtained by a positive pressure within the interior of the package.Also, for some applications, it may be desirable to extend the platenout essentially to the region where the sealing bars contact the film,in order to provide additional heat in the interior marginal portions ofthe film where the most severe stretching should take place in the finalsealing stage.

The completed package comprises a semi-rigid container shell (receptacle12) the interior of which is evacuated and sealed from atmosphere by aclosure panel in the form of stretched film 20 force-fitted against theproduct by atmospheric pressure. As shown in FIG. 7, the closure memberhas a portion extending out beyond a corresponding peripheral edge ofthe shell 12 to permit grasping of the extended portion to aid inopening the package.

Although preferred embodiments of the invention have been set forth indetail, it is desired to emphasize that this is not intended to beexhaustive or necessarily limitative; on the contrary, the showingherein is for the purpose of illustrating the invention and thus toenable others skilled in the art to adapt the invention in such ways asmeet the requirements of particular applications, it being understoodthat various modifications may be made without departing from the scopeof the invention as limited by the prior art.

We claim:

1. A hermetically sealed and evacuated package assembly adapted tocontain a perishable food product and comprising a cup-shaped containermember having peripheral flanges around its opening, said containermember being made of relatively thick, semi-rigid, gas-impermeable,light-transmitting plastic material adapted to provide substantialmechanical protection for a contained product, the upper surface of saidproduct being below the flanges of the container member at least in theregion adjacent the container side walls;

a cover sheet of flexible and stretchable gas-impermeable materialdisposed over said opening of said container member and sealed to saidflanges around the periphery of said opening to hermetically seal saidpackage from outside atmosphere, said flexible material beingsubstantially thinner than said semi-rigid container material andincapable of providing substantial mechanical protection for thecontained product, said flexible material being stretched downwardlyalong said container side walls and being held by atmospheric pressurein tight and intimate form-fitting engagement with said product entirelyacross the upper surfaces thereof; and

a relatively stiff protective member secured in position substantiallyparallel to said container opening alongside of said thin flexible coverand spaced a short distance therefrom, said protective member defining abottom element for the package when the semirigid container serves asthe protective top element in the normal upright position of thecompleted package assembly, whereby with the hermetic seal broken andthe package in the normal position with said semi-rigid container at thetop, the product within the container will move with said flexible filmdown towards said stiff bottom element providing a visible indicationthat the hermetic seal has been broken.

2. A package as claimed in claim 1, wherein an inert gas atmosphere isincluded within the package.

3. A hermetically sealed and evacuated package assembly adapted tocontain perishable food products or the like and comprising a cup-shapedcontainer member having peripheral flanges around its opening, saidcontainer member being made of relatively thick, semirigid,gas-impermeable plastic material adapted to provide substantialmechanical protection for a contained product, the upper surfaces ofsaid product being below the flanges of the container member at least inthe region adjacent the container side walls;

a cover sheet of flexible and stretchable gas-impermeable materialdisposed over said opening of said container member and sealed to theflanges of said contained member around the periphery of said opening tohermetically seal said package from outside atmosphere, said flexiblematerial being substantially thinner than said semi-rigid material so asto be incapable of providing substantial mechanical protection for thecontained product, said flexible material being stretched downwardlyalong said container side walls and being held by atmospheric pressurein tight and intimate form fitting engagement with said product entirelyacross the upper surfaces thereof; and

a relatively stiff protective member secured in position substantiallyparallel to said opening alongside of said thin flexible cover andspaced a short distance therefrom, said protective member being bondedto said flexible cover in the regions thereof which are sealed to saidcontainer flanges, the bond between said protective member and saidflexible cover being stronger than the seal between said flexible coverand said flanges, the stiffness of said protective member serving to aidin separating said flexible cover from said flanges to provide improvedopening of said package.

4. A package as claimed in claim 3, wherein an inert gas atmosphere isincluded within the package.

5. The method of making a hermetically sealed package comprising thesteps of:

inserting a product into a semi-rigid cup-like container with theproduct height being less than the height of the container side walls atleast in the regions adjacent said side walls; positioning over theopening of said container a cover sheet of plastic to form a packageassembly;

forcing said cover sheet in a direction away from the product in saidcontainer and towards a source of heat;

transferring heat from said source to said cover sheet sufficiently tosoften said sheet for stretching; evacuating the package assembly;

hermetically sealing the package with the cover sheet sealed to thecontainer; and

applying atmospheric pressure to the outside of said heated cover sheetto stretch the heated material in the regions thereof immediatelyinboard of the walls of the container defining said opening and therebyto effect a tight-fitting engagement of the cover sheet and the packagedproduct.

6. Apparatus for making packages comprising, in combination, a series ofreceiving elements adapted to be mounted in an endless loop arranged formovement past a series of packaging stations where sequential packagingoperations are performed, said elements including means to supportrespective cup-like members of semi-rigid material adapted to receiveproducts to be packaged; means to apply to said elements a film offlexible packaging material over the opening of each cup-like member insequence; a packaging head at one of said stations and including meansoperable to seal said film to the respective cup-like member in a regionextending around the periphery thereof; first vacuum means to withdrawair from the package and to reduce the pressure on the outside surfaceof said semi-rigid member during evacuation of the package; secondvacuum means to reduce the pressure on the outside surface of said filmduring said evacuation; a source of vacuum; first and second vacuumlines connecting said source to said first and second vacuum meansrespectively; control means for venting said source of vacuum after thepackage has been evacuated; and a check valve in said first vacuum lineto retain reduced pressure on the outside surface of said semi-rigidmember while atmospheric pressure forces said flexible film inwardlyagainst the product by stretching said film interiorly of said sealedregion.

7. In apparatus for making hermetically sealed and evacuated packagescomprising a series of receiving elements adapted to be mounted in anendless loop arranged for movement past a series of packaging stationswhere sequential packaging operations are performed, said elementsincluding means to support semi-rigid packaging material formed intocup-like containers carrying products to be packaged; means to apply acover sheet of flexi ble packaging material as a top over the opening ofeach cup-like container in sequence to make a complete package structurecontaining the product; packaging head means adjacent the path ofmovement of said elements and located at a position subsequent to thestation where said cover sheet is applied to the containers; saidpackaging head means including means to seal said sheet to each cup-likecontainer along a line extending around the periphery of the containeropening; the improvement wherein said packaging head means includes aheating element positioned to lie adjacent the outside surface of saidcover sheet and in a region thereof which is inboard of said peripheralsealing line; said packaging head means comprising differential pressuremeans operable to develop a first differential pressure across saidcover sheet to force it away from the product in the correspondingcontainer towards said heating element to effect a transfer of heat tosaid cover sheet so as to soften it for stretching, and operablethereafter to develop a second differential pressure in a reversedirection across said heated cover sheet to stretch the heatedmeateri'al thereof which is immediately inboard of said seal line so asto form marginal stretched portions which in the completed package areforced by atmospheric pressure into the cup-like container, along theside walls thereof, with the central area of the cover sheet within saidmarginal portions in tight engagement with the product.

References Cited UNITED STATES PATENTS 2,621,129 12/1952 Ramsbottom etal. 99171 2,834,686 5/1958 Reuman 99'17l 3,034,271 5/1962 Carpenter etal. 53184 3,079,057 2/ 1963 Calarusso 2293.5 3,196,590 7/1965 Ollier etal 53-112 3,226,236 12/ 1965 Weller 99171 3,298,158 1/1967 Schmidt5,3112 3,347,011 10/1967 Lovas et al. 5322 3,467,244 9/1969 Mahaffy etal. 20645.34 3,498,018 3/1970 Seiferth et al. 99-171 X 3,522,687 8/1970Mahaify 53-22 MORRIS O. WOLK, Primary Examiner S. B. DAVIS, AssistantExaminer US. Cl. X.R.

5322 A, 30, 39, 42, 112 A, 184; 99-171 LP, 171 TC, 171 LM, 189; 20646 F

